1. Field of the Invention
The present invention pertains to techniques for enhancing exchange processes between two fluids. More particularly, the present invention relates to packing elements for use in exchange process chambers, such as are utilized in mass transfer or heat exchange processes, for example.
2. Brief Description of Prior Art
Many commercial and chemical processes involve mass transfer or heat exchange, and utilize packed columns or chambers to carry out the steps. Such processes can include distillation, absorption and desorption, gas cleaning and drying, scrubbing and various biological processes, such as filtrations. Two fluids, usually a gas and a liquid, although two liquids may be utilized, are intermingled within a chamber, typically as counter-current flow streams wherein the two fluids move generally in opposite senses along the same flow axis. In a co-current system, the two fluids move generally in the same sense along a single flow axis; a cross-current facility features the two fluids moving along separate, intersecting flow axes.
The mass transfer rates and/or the reaction rates of the processes increase with increasing amounts of effective surface area that can be wetted by liquid within the chamber and over which the two fluids can then interface with each other. Packing elements are placed in the chamber to increase the amount of surface area available for such interfacing. Packing systems are generally of two types, depending on the packing elements and their arrangements in the transfer chamber. Structured packing systems generally include extended, structured packing elements that are arranged within the chamber. Random packing systems comprise generally small, individual packing elements which may be dumped into the exchange chamber in a random array.
Packing is generally included in exchange process columns to enhance the interaction between two fluids in the column, thereby increasing the efficiency of the process. Where at least one of the fluids is a liquid, the interaction between the fluids may be so enhanced by providing sufficient surface area to be wetted by the liquid, and providing drip points from which the liquid may pass from one surface to another while being further exposed to gas as the other liquid flowing between the surfaces. If the surfaces provided by the packing are too tightly-arranged, the gas may experience sufficient flow resistance to hamper movement of the gas through the packing, thereby diminishing the opportunity for exposure of the liquid to the gas. Poorly-designed random packing elements may feature significant mutually-complementary structures so that one such element may fit relatively tightly against another, or even extend within the lateral extent of the second element. Such nesting of random packing elements may produce a relatively tightly-packed array of surfaces, producing significant gas flow resistance. Further, where the liquid flow surfaces are too tightly packed, liquid may bridge from one surface to another without dripping. Not only does such bridging diminish the interaction cross section with the gas, but it may also further impede the flow of gas through the packing.
U.S. patent application Ser. No. 08/291,723, filed Aug. 16, 1994, which is a continuation of U.S. patent application Ser. No. 08/049,573, filed Apr. 19, 1993, now abandoned, and which issued on May 2,1995, as U.S. Pat. No. 5,411,681, provides random packing elements which avoid the aforementioned disadvantages of previously-available packing elements. The packing element disclosed in the '723 application is shown in FIGS. 1-4 herein, and comprises material forming strips extending between attachment areas and projections from attachment areas. The present invention provides improvements on such packing elements.